A replicated, controlled study in 1990-1994 of arable fields on 15 farms in the Netherlands (de Snoo 1997) found that unsprayed field margins contained higher plant diversity, abundance and more important/rare plant species than sprayed margins or fields. Species diversity was significantly higher in unsprayed edges than in sprayed edges (sugar beet: 24 vs 16 species/75 m², potatoes: 17 vs 8, winter wheat: 17 vs 6). Field centres had the lowest diversity (2-10 species/75 m²). Thirteen, nine and 30 species were found only in the unsprayed edges in sugar beet, potatoes and wheat respectively. Unsprayed edges had significantly higher floristic values (scoring system based on the importance of different plant species in terms of rarity) than sprayed edges: by a factor 5.2 in sugar beet, 2.8 in potatoes and 7.2 in winter wheat, values were lowest in field centres. The cover (biomass and height) of farmland plants was significantly higher in unsprayed compared to sprayed edges (8-52% vs 1-13%) and lowest in field centres (0-3%). A total of 5-20 fields were studied from 1990-1994. Strips 3-6 m x 100 m long along field edges were left unsprayed by herbicides and insecticides and were compared to sprayed edges in the same field and to the sprayed field. Vegetation was sampled in 75 m² plots in mid June to mid July. This study was part of the same experimental set-up as (de Snoo et al. 1994, de Snoo 1996, de Snoo & de Leeuw 1996, de Snoo et al. 1998, de Snoo 1999).